Part Manufactured using CNC Milling Services

CNC Milling Service

Get custom milled parts for rapid prototyping and production.


ISO 9001:2015 | ISO 14001:2018

Part of our CNC Machining Services, our CNC milling process produces custom CNC prototypes and end-use production parts in as fast as 1 day. We use 3-axis milling and 5-axis indexed milling processes to manufacture parts from more than 30 engineering-grade plastics and metals.

Our CNC milling service is commonly used for:

  • Functional prototypes
  • Jigs and Fixtures
  • Production components in lower volumes

Design Guidelines: CNC Milling 

Threaded Holes

Threading in CNC Mill Parts

We currently support UNC and UNF threads from #2 up to 1/2 in., and metric threads from M2 to M12. Avoid modeling internal threads on your part design.

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Text on CNC Milled parts

Recommended for CNC milling text:

• Recessed text should have a minimum stroke width of 0.5mm.

• The spacing between characters on raised text should be 0.5mm or greater.

• Minimum recessed text depth of 0.3mm.

• If design permits it, opt for recessed text versus raised.


Radii in CNC Mill Process

Sharp inside corners on a part will be radiused (rounded) as a natural result of the CNC machining process. Resulting radii will be identified before the part is milled.

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CNC Milling Materials

We stock more than 30 production-grade plastic and metal materials that are suitable for various part applications and industries.

CNC Milling Materials - Aluminium CNC milled part


  • ABS 
  • Acetal
  • HDPE 
  • Nylon
  • PEEK
  • PEI
  • PET


  • Aluminium
  • Brass
  • Carbon Steel
  • Copper
  • Mild Steel
  • Stainless Steel
  • Titanium

Anodising and Chromate Plating Specifications

Anodise Hard Anodise Chromate

Decorative Anodising | ISO 7599

Equivalent to - MIL-A-8625 Type II, Class 2 (Black)
MIL-A-8625 Type II, Class 1(Clear)

Hard Anodising | ISO 10074

Equivalent to - MIL-A-8625 Type III, Class 2 (Black)
Chromate Conversion Non-Hexavalent | SurTec(R) 650

Equivalent to - MIL-DTL-5541 Type II, Class 3 (Clear)


Quick-turn Finishing

Here are the requirements to get parts in as fast as 6 days (1-day expedite + 5 days for plating): 

  • Aluminium 6082 and 7075 material eligibility 
  • Threaded holes plugged 
  • No masking available 


High-requirement Finishing

If you have more complex anodising and plating requirements, work with our digital network of manufacturers. The network works well for components that require a specialised colour or material option such as titanium or nickel.   

CNC Machining for Aluminium Part

Aluminium Alloys

Aluminium offers excellent machinability, durability, low weight, and low cost for a variety of parts in a variety of industries.

Designers and engineers frequently choose aluminium and aluminium alloys for CNC machining and CNC milling parts.

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Surface Finish on CNC Milled Parts

Typically, we break (debur) the edges on all machined parts. All machined plastic parts are left as-machined, which may leave visible tool marks. Some metal parts, on the other hand, allow more choice. Parts left with sharp edges should be handled with care.

ABS Black Plastic CNC Milled Part, sharp edges removed
ABS Black

Finish: As machined with sharp edges removed

Aluminium CNC Milled Surface Finish on Metal Part, sharp edges removed


Finish: As machined with sharp edges removed

CNC Milling in ABS Natural Plastic, sharp edges removed

ABS Natural

Finish: As machined with sharp edges removed

Aluminium CNC Milled Metal Surface Finishes, Light Bead Blast


Finish: Light bead blast


CNC Machining, process and capability

Protolabs is the world's fastest source for custom CNC prototypes and low-volume production parts. Our high-speed CNC machining service uses advanced CNC technologies to create parts ranging from highly complex prototypes to functional, end-use parts. A range a plastic and metal materials are available through two CNC machining processes: milling and turning. Get 1 to 200+ parts in as fast as one day with CNC machining at Protolabs.

About CNC Milling


What is CNC milling?

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CNC milling is a subtractive manufacturing process, 3-axis and 5-axis indexed cutting tools are programmed and managed by computer numerical control (CNC), removing material from the plastic or metal block

CNC Milling design guidelines will help you understand capabilities and limitations.

How does CNC milling work?

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How CNC milling works

The components of a CNC mill include: end mill & tool holder (1), tool changer (2), tool carousel (3), spindle (4), 2-axis milling head (5), air/coolant supply tubes (6), fixture (7), work piece (8), tool setter (9), x- and y-axis table (10).

We have multiple tool sets based on efficient cutters for a particular plastic or metal material. The machine then rapidly mills parts out of the block in a subtractive manufacturing process that uses 3- or 5-axis indexed milling.

Machined plastic parts are left as-milled, which typically means they show visible tool marks. Some metal parts allow more finishing choices. When the run is complete and your required surface finish is applied, parts are boxed and shipped shortly thereafter.

Why use CNC milling for your project?

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Protolabs’ CNC machining service can deliver machined parts, in both plastic and metal, in less time than it takes to get a quote from other, more traditional machine shops. Upload a CAD file, choose the material and part quantity, and tell us when you need the parts. We also offer number of CNC specific secondary services to support your project.

CNC material data sheets can be found in our Material Comparison Guide

What are the benefits of CNC milling?

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  • Good Surface Finishes
  • Very Strong (because they use real engineering-grade thermoplastics and metals)
  • Fast Parts
  • High Accuracy Parts

What are the applications of CNC milling?

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CNC Milling is a very versatile process that is used in most industries. It is most notable for producing precision parts in particular for automotive and aerospace industries. Parts such as engine components, bushings and exhaust parts. It is also a key service for medical componentry, supporting with prototypes in particular.

It is an important technology in the Oil and Gas industry for key components in extrusion and for Industrial Equipment such as jigs, fixtures tractor parts etc.. This is due to its ability to create complex, accurate, high-finish, high-tolerance parts. It's threading possibilities are also key.

Finally it's high-precision, light weight metals and high-performance plastics make it a popular choice for the aerospace industry for many exterior structural parts and interior parts for bearings, wall panels, ventilation ducts etc. 

What can CNC milling offer you?

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CNC milling is often associated with parametric, or cubic designs (and turning with cylindrical) but there is a lot more available:
• Contoured Surfaces - Using a ball end milling cutter and modern CAM software some really complex contoured surfaces are available, even with 3-axis (the kind that you might associate with 5-axis or 3DP)
• Complex Detailing - Engraving and text, by using a small tool, even surface patterns and finishes can produced (often used when producing mould tools)
• Threads, both 3D printing and injection moulding struggle with threads, but CNC can produce 100’s of threads (and is even used to produce inserts used for injection moulding)
• Pockets - These can be used for light-weighting. New design tools for weight optimisation are focused on 3D printing, but they can just as easily be applied to CNC, just remember to design for tool access and add generous fillets.
• Finally walls - Bosses and raised Features can all be created, but remember subtractive (engraved) features like slot slots, channels and holes, are normally more cost effective to machine away.

How much does it cost to manufacture CNC machined parts?

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There are 4 key factors that contribute to your parts, raw material, machine time, labour and speed.

It will be no surprise that some materials are more expensive than others, for metals, steel and aluminium are abundant and have the lowest raw material cost per kg whilst for plastics Acetal, Nylon, Acrylic and ABS tend to work out cheaper.
In the middle of the spectrum for metals you have more specialist aluminiums and stainless steels (containing expensive alloying elements) and for plastic glass-filled grades.
At the high-end you have materials like titanium (which is abundant but difficult to refine) for metal and plastics such as PC, PEEK, PPSU, PEI and POM-ESD, generally required to meet a specific need.

Things such as part complexity and material machinability play a factor here and of course the quicker you want something the more you are likely to pay, remember to compare costs like for like, considering both price and delivery. 

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